Quirk Booster
by GhostiesAndHoes
Summary: After a virus is created in the school grounds that boost an individual's quirks, unexpected side effects appear and our heroes are trapped in the school fighting for their lives. Many have died and Deku, Todoroki and Asui have to make it to the end of the week. They'll have to face their former friends and allies who have gone insane.
1. Part 1: 3 days left

《{Author note}》

Hi this is my first work on here

i hope you like it. I'll definitely finish this but i might do a different story genre and setting each time. i know the start is trash but please read till the end.

Deku was sitting at his desk while Eraserhead was mumbling something about algebra. Everyone was daydreaming and it seemed to be a normal day.

"Ok class. Class as you all know the science department has been working on a quirk boosting method for sometime."

"How is anyone supposed to make my quirk any better? Hehe" mocked Bakugo.

"So is it going to make us stronger?" Asked Mina.

"It works similarly to a virus right now. It significantly boosts the power of someone's quirk and it can be passed on to other people." He explained.

"So this class has been chosen to be the test subjects. You will be living at the school for a week so we can monitor how your doing."

The class moaned. The idea of staying at school longer than they had to was horrible.

"You'll still do work during the normal school hours but after that you can do whatever you like. Class dismissed."

As the students left the class Deku was already overthinking everything. He hoped he could finally master one for all otherwise he'd possibly die.

~Two Days Later~

Deku heard screaming. Another person probably being chased through the halls which were covered in blood. A grim reality had befallen our remaining heroes. Deku, Todoroki and Asui were the only ones who hadn't been affected. Maybe they were immune. Deku felt brave. He stepped out of the class, he needed to go get some food. He stared down the hallway, peering into the darkness. Red eyes were glowing, a grim smile could be seen. Uraraka shot forward lunging at Deku. She made herself float and gained significant speed as she left the darkness. Deku used full cowl and ran in the opposite direction. He called out for Todoroki for help. Behind her was hundreds of different weapons that were made by Creati who died after the first wave. Murderous intent flowed from her. The virus had been named QuBo but one of the side effects was it made subject go manic. She shot a few weapons at Deku, Todoroki slid in quickly and blocked her with an ice wall as they turned a corner. Deku tripped over the body of ectoplasm. It's impossible to know when he'd been killed.

Asui was waiting for them in the cafeteria. They locked every door and barricaded the windows. They might have to live there. if you could call constantly running in fear _living_. After the first villain attacks the school had upgraded their security system to withstand all quirks so even Deku's full cowl was useless.

"HAHAHA. LOOK WHO SHOWED UP TO THE PARTY. THE REMNANTS OF CLASS 1-A! I thought you guys were supposed to be the best. The all mighty rulers of UA!" they could hear this voice but couldn't see who it was coming from. Then they heard the same voice speak in an evil tone.

"kill em. Break their bones. Rip their skin off. I want to write the 'death of UA' across the school with our finest students' blood."

Monoma came out of the shadows standing on top of one of the tables. Him and his goons had been hiding in an underground bunker that one of them had supposedly made. he seemed a lot more controlled than the other students that had been affected. Almost half of class 1-B dashed across the hall towards the surviving unaffected students. All of them petrified.

"What are we gonna do? we could only beat them if we took each one on separately." panicked Deku.

"WELL I DOUBT WE CAN ASK THEM TO NICELY FORM A LINE WHILE WE PUMMELD EACH OF THEIR ASSES ONE BY ONE." exclaimed Todoroki, he was frustrated. Deku was supposed to be the great strategist.

"Well it was nice knowing you guys." Asui said in a worryingly calm voice. She used her tongue to propel herself to one of the bars on the ceiling. She wasn't even up there for a second before being smacked down by Kendo. Almost as a reflexive response Deku transformed into full cowl again and started punching through the crowd. Todoroki supported him with flames and ice on either side of him. Asui was crawling on the floor, hoping that no one would bother with her after seeing her be knocked down. Kendo pridefully walked over and raised an over sized fist with a chuckle.


	2. 2: Still 3 days (minor)

Author's note: i know. i know. you hate me. I still love you though. Sorry it took so long. I've been watching anime. give me another series to write about and i'll consider it. Enjoy!

Deku fought through the wave of students in front him. Charging through the mindless zombies, his power releasing more rapidly the closer he got to Asui. He grabbed Kendo and pushed her aside, his eyes were glowing in a way his friends had never seen before. Even in their altered states all of the infected students stopped to stare at Deku.

"This is my school. I worked hard to get here. These are my friends. All of us. So if I have to rip you apart so we can stay together... I'll do just that" there was a malice in Deku's voice as he said this, it wasn't the same as the people who had been taken over by QuBo.

Glass shatters. Kendo had attempted to push Deku back but he returned the force of her attack ten fold and sent her flying backwards. Asui had gotten up despite her obviously injured legs.

"Guys. I'm sorry. I was scared." She pleaded with them, they stayed silent and mentally agreed to talk about it later. Deku's power was still rising he decided to head straight for the leader of the wave of vagabonds coming towards him.

Monoma had no plan, he grabbed a hold of Deku and instantly copied his quirk, however he started making small fire balls as if he was playing with them.

"Do you like my new trick?"

Todoroki shot an icicle straight at his head but a flame shield melted it out of existence. All might's successor was smashed into the ground.

"Ah. You guys are supposed to be giving me a challenge. If you want I'll go find ya girlfriend and cut her lips off so you can give her one last smooch" mocked Monoma. Deku hooked his feet behind the goon leader's and made him fall on his back. He then grabbed him by the legs and swung him into the chairs and tables.

"Ok. Let's go"

They sprinted towards the door they came though and turned a different direction. They were heading for the staff room. Rumour had it that there was a panic room for emergencies.


	3. Still 3 Days Major

Authors note  
So the major minor thing isn't going to be reoccurring, i just did that because I didn't have time to right the whole thing. Also if you can draw or animate inbox me, i have an idea. As always I hope you enjoy and tell me what I did wrong.

The staff room had somehow remained mostly intact. There was a few things displaced but other than that nothing had changed. "I think we'll be safe here" wheezed Deku.  
"Are you ok Deku" asked Todoroki  
"I'm fine"  
They searched for the hidden door to the panic room and couldn't seem to find anything.  
"where would an entrance be in a room as open as this?"  
They could hear scratching and shouting on the other side of the door. it wasn't gonna last forever. They had to move quickly or else they would have to succumb to the horrible Insanity that was on the other side of that flimsy piece of wood.  
"Come on Einstein we need to find that door!" snapped Todoroki.  
Deku was intently staring at the group photo of all the staff on the wall. He looked at his old teachers, and a great pain struck him, the dawn of his reawakening.

He stood with a spirit of failure but a lingering will to improve.

"I've failed them. I let them all down. i won't let you down too."

A swift thrust to the photo pushing it backwards with a hiss.

...

There were a few clunks and jolts, the room vibrated. but nothing seemed to happen.

"That's all?" inquired Asui.

Before she could finish her sentence the room rapidly descended into a deep dark pit that was slowly lit by the florescent light bulbs that hadn't been turned on since they were installed . A large crate appeared in the centre of the now expanded staff room. The team rushed to inspect it and it was filled with enough food to feed 30 people well.

Deku let out a sigh of relief and collapsed on the floor into a deep sleep.

For now our heroes were safe. But will it be short lived? Find out next time!

(if i can maintain my horrible upload schedule lmao)


	4. 2 days left

~GUESS WHOS BACK. i have mastered the art of the fanfiction writer. This one is gonna be longgggg so sit back grab some pocky, grab your body pillow and enjoy~

Deku's Re:Birth

2 Days left

The ambient lights of the panic room calmed Deku as the filtered through his reluctant opening eyes, knowing that he was still with his friends and that for a little while he was safe was reassuring. Todoroki was in the corner brooding and Asui had grown quite fond of the teachers chair and desk. From now on things would be simpler. They only had to wait until the gates opened then they could escape, back to the world. Deku was sure his mother was worried about him.

"So what happens in two days?" asked Asui.

"Well the metal shutters around the school will open automatically and we can get out of here. We c-can go home." replied our protagonist.

Unknown to Deku or Todoroki Asui didn't have a home to return to. Her parents had left for another country, it was unlikely that they'd ever hear about this. Some part of her hoped that they would be home to surprise her.

"Once we get out… i'm never coming to school again… i'm going to become a rogue hero."

Todoroki announced in a low rough voice. The fire and ice prodigy was ready to never see a school building again despite all he had seen during this atrocity there was still a blaze of hope deep in his spirit to be a hero, even though sometimes he didn't show it. He still wanted to save people.

"Once this is over… I'll help everyone affected by the virus!" Proclaimed Deku. Even if hope was beginning to fade he couldn't break the promise he made to his mentor, especially not when he died protecting him. All Might sacrificed himself and was killed by the hand of him. No matter the consequences, obstacles or challenges Deku would avenge the death of All Might.

"I think we should try it out Deku, you never know till you try it. I did it with my dad and he lov-" Asui stopped. She looked at her phone. It was a message from iida. HELP! Asui showed everyone the text.

"How is he still alive?" she said astounded.

"He's fast enough. My guess is he just kept running." smirked Todoroki.

"We have to help him!"

"Well we could. But if we do we'd have to leave here. I've come to like this corner of mine. Also are you sure we're prepared to fight through waves of fellow students?"Deku was already at the door. "if you guys come or not is up to you. But i will never leave a friend behind." his inner hero was beginning to shine.

"I guess that settles it. Show us the way O fearless captain" Todoroki chuckled.

Deku pressed the release button and the room began to rise, the same gears and pipes all in a harmonious discord. The platform was raised up into the staffroom again. Whoever was was on the other side of the door last night had obviously either gotten bored or had been killed by something bigger. They opened the door and step foot into the hallway. Something was wrong. There were not the usual screams of laughter from the class 1-B students or the growling of the the animal quirk students. It was a painful silence. Something had taken over the atmosphere creating a new sense of malevolence. It was as if the air itself wanted to kill you.The hesitant hero team crept down the hallway but as they approached the end of it they heard scuttling.

A wave of infected students came crashing from all directions, flooding the hallway. Deku shouted "WE DON'T HAVE TIME TO FIGHT ALL OF THEM LET'S JUST RUN THROUGH." The group did as instructed and they formed a line behind Deku and ran down the left side of the corridor. "Iida said he's in our homeroom!" shouted Asui.

In the home room Iida was facing a new threat. Since he had no orange juice to power his engines he had to stop running. He was forced into cowering under the lowly school cleaner. The school janitor had been infected by the virus and of course he wanted to kill Iida. The janitor's quirk was the ability to create metal. He made a trident similar to the devil's own out of gold. "Oh come on little engine boy. Don't be sad. We are all one under QuBo. your powers could be useful to our Prophet. Maybe he'll make you a delivery boy! Hehe" the janitor taunted in his unsettling voice. Iida's engines spluttered, no more power to draw, he'd ran out of juice a day and a half ago, he was running on empty. Iida started to think on all that had happened in the past year. His brother was paralyzed, he got into hero school...he met Midoriya. Is this his end? It didn't feel like he was worthy of it.

*smash*

"KNOCK KNOCK IIDA-KUN… oh you have company? We can leave." Shouted Todoroki.

The janitor turned around and smiled sinisterly. "Yes. i'll be happy to present you to the Prophet as well. Mwhehehe." The janitor threw knives at the three students. Without hesitation Deku awakened one for all and smashed the fodde- i mean janitor into the the wall behind him. Unlike the other times Deku has used his quirk where the opponent has been knocked out or been barely damaged, this time they were killed. The impact of the janitor hitting the wall created a crater. His blood dripped off the wall. Iida stood and thanked Deku.

"Guys… i just killed someone." whimpered Deku

"Yeah so? There's been hundreds of deaths this week. All of us have killed someone right guys?" Todoroki tried to reassure Deku but the rest of the the squad immediately disagreed with him. Deku refused to dwell on it however. Unbeknownst to him, his quirk was changing.

"Wait. i can't turn off Full cowl." Deku's worry increased

"You'll be fine. You're just stressed. Quirks are weird like that." said Todoroki.

Deku was calmed by Todoroki's words. They all headed back to the panic room to have some rest.

There's only one day left. Will they survive? Find out next time on the jeremy kyle sho- i mean this fanfiction.


	5. The Last Day

(Author's note: I'm sorry. This is hard. But this dumb story has over a thousand views now so i gotta complete it. I might do a black clover story next or actually finish my boruto one. but whatever happens next its probably gonna be better. Thank you!)

The Last Day

Deku's full cowl was still activated even after he slept. It was the final day they would be trapped in the school until all the gates were opened. One of Deku's recurring concerns was what would happen to all the students affected by the virus. Would there be a cure? Would they be contained there forever tearing each other apart? What would happen to his friends? These are questions he couldn't answer. The gates were opening at midnight so the plan was to survive just a little longer and escape. Deku was the first to wake up everyone else was asleep they seemed especially tired.

"Oh you're awake. Mr Deku. The replacement of All Might." an unknown voice said in a hush tone. Their face appeared from the shadow opposite Deku's bed.

"EVERYONE WAKE UP!" Deku shouted but they couldn't hear him.

"Ha. waste your lungs in futility." their voice appeared seemingly more female.

"Its my quirk. The eternal sleep. I can force a target to sleep for an endless amount of time, i can also manipulate their dreams into nightmares. Your friends won't wake up until i let them." she explained.

"Why didn't you put me to sleep?" asked Deku.

"Well i wanted to talk to you. Even though i've been infected by QuBo I haven't lost my sanity. Well… not all of it. I snuck in here and hid when you went off to save Iida." she continued

"What could we possibly have to talk about?" Deku was curious but at the same time cautious.

"A few things. I put your friends to bed for more than just some alone time with you darling. You see, people who are infected are way less likely to attack someone who is also infected, they require pure blood to be satisfied. I'll let you think about that. Another thing is you need to meet our Lord. He's the one who decides the fates for each and every person in this school and he requested to see you. That's all cutie. Your friends will wake up in about two hours." the person finished their speech. Deku had so many questions but before he could open his mouth she vanished.

-In Todoroki's Nightmare-

A large hand was chasing him with smaller hands on top of it. His father's face appearing in flames that lit the path to an enormous flame shaped like a gate to the hospital his mother was kept in. Todoroki ran off the path into a pit of ice, burning hot ice that somehow felt disappointed in him each time he touched it. The sun was covered by a shadow that spelt the name Deku. There was no end in sight. He screamed aloud but he had no voice. He tried to cover his face but it melted in his hands.

-In Asui's Nightmare-

Asui was finally home. Her parents had returned home and were sitting at the dinner table. Asui went to join them but before she sat down her father said

"Who are you?"

"Asui. y-your daughter?" she stumbled.

"I don't have a daughter." he said.

Asui was confused at what he meant.

"Only a disappointment." he continued.

-In Iida's Nightmare-

Iida kept trying to run but the more force he put into his legs the heavier they became. A shadowy figure wearing his brother's costume was rapidly approaching.

"YOU AREN'T FAST ENOUGH TO CARRY ON MY LEGACY. THE HERO KILLER DESERVED BOTH OF OUR LIVES. YOU'RE WEAK!" the figure hissed at Iida as he failed to run. His feet were now stuck in the floor as he began sinking into his doubts. He thought of class 1-A, All Might and Eraserhead. He thought of how they've all proven themselves to be great heroes yet he seems to only serve as a burden.

Midoriya could hear the struggle of his friends in their nightmares, he hoped that they would be safe.

A few hours passed and eventually they woke up. They had no time to waste so they immediately headed for the science lab where the aforementioned Lord was waiting.

Deku was effortlessly punching through the infinite amount students flying at him, since he couldn't deactivate one for all he thought he may as well master it. Todoroki, Asui and Iida were doing their best to keep the zombie-like creatures away from them. Todoroki looked down the hall and saw Uraraka with her cyclone of of objects forming around her.

"We should probably speed up" he said in his usually calm voice.

"You deal with the ones behind us." replied Deku.

The only solution he could think of was creating ice walls to block the paths of the attackers.

They finally reached the room of the so called Lord and Deku finally realised who would be arrogant enough to call themselves a door had had blood on the window.

"Someone tried to get out of here but whoever is in there...killed them.." said deku in horror.

"We're a team Deku. if anything happens we got your back." Asui said as Iida and Todoroki were looking for a way out.

Our brave heroes stepped into the room. The Lord was sitting on a throne made of infected students who were loyal to him till death.

"My God. Its true.. You were alive all this time... " the Lord said in a hush tone.

In an instant Deku realised it was a mistake to come here. He had hoped that maybe whoever the Lord was they'd be able to offer support or they'd want to leave with them.

"Bakugo."

"Did you miss me baby All Might? You're probably wondering how i survived or if i'm infected. The answer to that is murder and I'd very much like to show you."

Bakugo started charging his AP shot, Deku had no choice but since full cowl hadn't turned of he was already prepared.

"Do you need any help Midoriya?" asked Iida.

"...No. I knew this would happen." he replied as he rushed at Bakugo.

"Oh you're fast. But can you dodge this?" he said as he moved out of the way and released a rapid fire of impossibly large exploding projectiles. Deku couldn't get out of the way out of all of them so he was inevitably hit. Bakugo kept firing endlessly. Deku had an idea. He created a windstream to protect himself. They exploded on his makeshift shield.

"Oh come on show me the power of being a prodigy." Taunted Bakugo.

Deku saw an opening. He dashed towards Bakugo not guarding himself, his costume was getting ripped up by the explosions. Bakugo saw the opportunity and stopped firing to strike Deku.

"Gotcha!" they both exclaimed.

Deku ducked under Bakugo and smashed him to the floor.

"Wow. I can't really act surprised. Of course you were gonna beat me."

Before Deku could reply the sirens for the gates opening. Deku and the others ran outside to the gates. They were open. They were free.

 **4 months later**

"The QuBo Tragedy at UA high school has been finally been fully taken care of, although the students who were involved in this horrific event cannot wash the stains of the painful memories. The total body count is still unknown to the public but will be revealed once this investigation is over." stated the news reporter.

Deku, Asui, Todoroki and Iida were all continuing with their lives. But it was far from easy.

 **The End.**

 **Or is it?**

 **if you favourite maybe it won't be**


	6. Aftermath

QuBo: The aftermath

POV: article writer Jay Lemins

It's been about a year since the horrific incident at U.A highschool. The students who survived have mostly been treated from the strange disease that infected them. I find the different ways students survived quite interesting. One of the students Toru Hakagure, who has an invisibility quirk claims that she simply walked naked around the halls, another Momo Yaoyorozu had to constantly fight for her life by creating weapons with her quirk. Most of the students infected by the strange disease have been treated, some however were too aggressive/too powerful to be contained so they had to be neutralised in order to prevent further damage to the school, the other students and themselves. The most notable of these would be Katsuki Bakugo. He managed to hold off special forces for an entire extra day, preventing them from entering the campus. He even resisted the powerful mind control of the renowned hero Nekamaku. But after he was finally tranquilised, it was discovered that his exposure to the disease was minimal if there at all.

Deku was sitting at his lunch table with Iida. They were talking about video games and his mind seemed to wander for a second. He looked Iida directly in the eyes and without saying a word they understood each other. Deku couldn't shake the feeling something was around the corner, something big. Even though the QuBo incident felt like it was the worst thing that _could_ happen, deku was sure it wasn't. They were at a temporary school that was for regular students, they got the bus like regular students, they ate lunch like regular students but nothing ever felt regular. They were famous as the QuBo kids, people always had a sorrowful look in their eyes. It felt like their lives had been taken away despite the fact that they were still living and breathing. People always said they felt sorry for them for going through such a hard experience but they didn't understand what it was actually like. The repairs and renovations had almost been finished at U.A and since they hadn't finished their hero exams they were offered a chance to re-enroll at the school to finish them in the coming weeks. Deku was tearing himself apart trying to decide if he wanted to be Baby All-Might or Deku the hero or just Deku, a boy that admired heroes and respected the work they put in.

Some people handled the incident differently, Mineta was drowning in girls and was loving every second of it despite the fact he hid in a storage closet for a week, surviving only on water he'd drink in the toilets at night. Todoroki had finally accepted his duality and saw it as a chance to be a hero like his dad but better, he wasn't only the flashy hero you see on TV but a hero to the sick and to the poor. Iida only used his quirk in sports activities and Asui was almost content with being a normal student.

But Deku was right. There was something coming. Some scientists were able to extract the disease from less powerful infected students and in an attempt to find a cure, a vial was stolen, meaning that someone out there just became the most dangerous criminal on earth.

A threat much bigger than they could ever imagine was around the corner. But are they prepared?

Author's note: I'M BACK. I missed writing something creative so thanks for the views. If you like goofy stuff tell me and also check out my instagram slutty_puttyy


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